Efficient and selective preparation of organic molecules is critical for the synthesis of therapeutics. Many of the most proficient known processes depend on the availability of catalysts. One of the advantages of organometallic catalysis is the ability to tune the activity and selectivity through modification of the ligands around the metal center. Recently, major advances have been reported thanks to the use of electron-rich phosphines and cyclic diaminocarbenes. We have uncovered several novel families of stable carbenes, such as the cyclic (alkyl)(amino)carbenes and the diaminocyclopropenylidenes, which behave as even more electron-donating ligands. They have already allowed for improving known palladium and ruthenium catalyzed processes, and even for promoting new metal catalyzed reactions. The full catalytic potential of complexes bearing these carbene ligands will be investigated. In order to obtain even more robust and efficient transition-metal catalysts, novel types of carbon- based ligands, which surpass the electron donating properties imposed by any other ligands, will be prepared. Special attention will be drawn on families of ligands for which it will be possible to precisely tune the steric and electronic parameters. There is a high demand for technology to produce therapeutics in a pure enantiomeric form, thus optically active versions of our new ligands will be prepared. The studies will be focused on catalytic processes for which real difficulties remain, and on chemical transformations, which have not yet been achieved, but are of critical importance for building the skeleton of complex molecules. Cascade reactions that involves several reactants, yet a single catalyst, and which lead to biologically relevant heterocycles and to important synthons will be developed. To accelerate the widespread implementation of our ligands, we have already formalized a collaboration with Robert Grubbs at Caltech, and we are looking forward to further partnerships. The ultimate goal of this research effort is to find truly practical catalysts, and catalytic reactions, which will find applications in both industry and academia for the selective synthesis of biologically important compounds. )